Surface Wind Modification by Sea-Surface Temperature Fronts: Satellite Observations and Implications for Coupled Air-Sea Interaction Processes

As winds blow across eddies and ocean current meanders with spatial scales of ~100-1000 km, surface winds are stronger over warmer water and weaker over cooler water, with the net result that winds and sea-surface temperature (SST) are positively correlated. Evidence is emerging that a realistic description of this coupled wind-SST interaction is crucial for models of local and large-scale atmosphere and ocean circulation. In this talk, satellite observations of this coupling are explored over several large-scale frontal systems of the mid-latitudes and the eastern tropical Pacific. This wind-SST coupling observed from satellite is shown to compare well with that observed from moored buoys, demonstrating the capability of satellites to adequately describe this coupling. In addition, these satellite observations show a strong seasonal pulsing of the SST-induced surface wind stress, with the most intense stress perturbations during winter. It is shown that this seasonality is caused mainly by seasonality of the large-scale surface wind speed through nonlinear amplification of the SST-induced surface wind speed.

These observations demonstrate the need for improved representation of mesoscale wind-SST coupling in Reanalysis surface wind fields; continuous, high-resolution monitoring of surface winds and SST from satellites; and improved understanding of the feedback onto the ocean from the SST-induced wind stress.